1. Field of the Invention
This invention relates to methods and apparatuses for the control of sand, formation particles, and other contaminants in a wellbore and particularly to devices and processes for protecting wellbore packers and other operative mechanisms from the deleterious effects of particulate contaminants.
2. Description of the Prior Art
Many attempts have been made to develop a method to keep sand out of a well, out of the fluids produced from a well and away from the various mechanisms in a producing wellbore. Where sand problems are common, control of sand is a necessity. Sand movement occurs in numerous types of geologic formations including the shallow formations of the Tertiary age and in depths above 12,000 feet. Sand infiltration is the primary cause for a major percentage of repairs necessary to maintain or improve production from wells. Formation sand causes the plugging of tubing, perforations, and devices within the well and erodes and damages wellhead and production equipment.
Conventional sand control methods include the pumping of fluids to the bottom of the wellbore. These fluids and their components can damage the formation and reduce production. Fluids such as drilling muds, completion or workover fluids, and reservoir fluids often contain solids which damage the formation or they contain chemicals which cause an injurious chemical reaction between the fluid and some component of the reservoir of formation.
Gravel packing is a conventional sand control technique. The two major types of gravel packing are conventional gravel packing and washdown gravel packing. In conventional gravel packing a working string is introduced into the wellbore with a gravel pack screen at the bottom of the string. A shorter screen called a "tattletale" is placed above the gravel packer screen. The gravel pack material is pumped down the working string to surround the screen and pack the annulus between string and wellbore in the area of the perforations which extend into the producing formation. Once the packing has reached a level above the tattletale, pumping is stopped. Prior to commencing production, the working string is removed from the wellbore and a production string is inserted. A packer is used to fill and close-off the space between the interior of the casing and the exterior of the production string so that produced fluids will flow up the production string rather than up the space between the casing and the production string.
In washdown gravel packing the wellbore is filled with a desired amount of gravel pack material, usually at least to a level above the perforations. The tubing string used to pump the packing is removed and a production string having a gravel pack screen at the bottom and a wash pipe therein is inserted into the packing. Water flowing down the wash pipe washes the gravel pack material out of the way to permit the screen and string to descend to the desired depth in the packing. This is necessary because the gravel pack material, due to its high coefficient of friction, presents a relatively "hard" surface to the screen. the wash pipe must be removed prior to the introduction of a production string. Again a packer is used to close off spaces in the interior of the casing and tubing to insure that produced fluids flow upwardly as desired.
When a string having a not-yet-activated packer is emplaced in a wellbore to the depth of a producing formation, and particularly when such a string has a filter such as screen attached at its bottom and is washed into place, various problems are encountered because of the flow of particulate and contaminant-laden fluids past the packer. The packer is activated to insure that produced fluids flow upwardly as desired rather than, e.g., between the casing and the tubing. However, solids and other contaminants in fluids passing the packer can clog and erode its parts, including operative mechanisms which must operate when and as desired to make the packer set, seal and seat properly. A malfunctioning packer can inhibit or prevent production and it is a very expensive process to retrieve such a packer from a wellbore.
In accordance with .sctn.1.56 of 37 C.F.R. applicant is aware of the following prior art, copies of which are submitted herewith:
1. N-SITU TECHNOLOGY, Section 3, Baker Sand Control, 1984-1985 Catalog, pp. 23-50, 55-56. PA0 2. Introduction to Oil Well Service and Workover, published by The University of Texas, p. 23, 1971. PA0 3. Workover Well Control, by Adams, pp. 4-11. PA0 4. Halliburton Services Sales and Service Catalog, 1970-1971, pp. 130-136. PA0 5. Casing Hardware and Oilfield Service Tools, Dowell, 1982-1983 Composite Catalog, pp. 2520-2523. PA0 6. U.S. Pat. Nos.: 50,967; 58,953, 83,901; 963,549; 1,974,664; 2,216,037; 2,321,318; 2,356,769; 2,513,944; 3,351,475; 3,587,740; 4,549,608; 4,550,778; 4,552,215; 4,552,216; 4,553,595.